Field of the Invention
Embodiments of the present invention generally relate to small antennas suitable for mobile devices operating in the high frequency and radio frequency bands in the range 100 MHz to 5 GHz.
Description of the Related Art
Reduced size portable devices that require radio communication in the 100 MHz-5 GHz spectrum are facing problems related to the design of appropriate antennas. There are fundamental and practical limitations when antennas operating in such spectrum need to fit a small physical volume. The result is insufficient level of radiated power and poor receiver sensitivity. Both these problems are related to the antenna radiation efficiency being too low.
State of the art antenna design techniques are able to mitigate such issues using specific broad band or multiple resonance antenna designs. These techniques are able to solve some of the specific design problems related to a particular device, but are still falling short of providing a generally adoptable antenna design technique that can meet radiation related specifications within the constraint of a small antenna volume.
Therefore, there is a need in the art for a technique to tune the antenna resonance frequency of a certain band of a multi-band antenna by means of an electromagnetically coupled parasitic element coupled to a variable impedance device without affecting other bands of the antenna.